Ruby rails. Undefined method error, creating nested resource object - ruby-on-rails

Question

I am trying to render a form to upload a song.
I have a playlist model and a song model, song being a nested resource of playlist.
With simple form, when I try and render the new song partial, I get undefined method songs_path for #<#<Class:0x007fdc51980870>
In routes, the new song path is new_playlist_song but it doesn't seem that simple form knows this.
Songs controller:
class SongsController < ApplicationController
def new
#song = Song.new
end
def create
#song = Song.new(song_params)
if #song.save
flash[:info] = "Song uploaded sensually"
redirect_to user_path(current_user)
else
render 'new'
end
end
def index
#song = Song.all
end
private
def song_params
params.require(:song).permit(:audio)
end
end
Playlists controller:
class PlaylistsController < ApplicationController
before_action :find_playlist, only: [:edit, :update, :destroy]
def index
#playlists = Playlist.all
end
def new
if user_signed_in?
#playlist = current_user.playlists.new
else
redirect_to(root_url)
flash[:danger] = "You have to register to purchase gigs"
end
end
def create
#playlist = current_user.playlists.new
#playlist.user_id = current_user.id
if #playlist.save
redirect_to new_playlist_path
else
render 'new'
end
end
def destroy
#playlist = Playlist.find(params[:id])
if #playlist.present?
#playlist.destroy
redirect_to playlists_path
end
end
private
def find_playlist
#playlist = Playlist.find(params[:id])
end
end
Song model:
class Song < ActiveRecord::Base
belongs_to :playlist
has_attached_file :audio
validates_attachment_presence :audio
validates_attachment_content_type :audio, :content_type => [ 'audio/mp3','audio/mpeg']
end
Playlist model :
class Playlist < ActiveRecord::Base
belongs_to :user
has_many :songs
end
Routes:
resources :playlists do
resources :songs
end
User profile link to create new song:
<p> <%= #user.playlist.user_id %> </p>
<p> <%= #user.playlist.created_at %> </p>
<% if #user == current_user %>
<p> <%= link_to "Uploaad track", new_playlist_song_path(#user) %>
<% end %>
I have tried a few variants for the simple_form form.
New song partial 1:
<%= simple_form_for ([#playlist, #song]) do |f| %>
<%= f.file_field :audio %>
<%= f.button :submit %>
<% end %>
another try :
<%= simple_form_for ([#playlist, current_user.playlist.songs.build]) do |f| %>
I just can't get the form to show and I can't figure out why not. Any ideas would be appreciated, thanks.

Answer 1

As pointed out in the comments songs_path is not referenced in your code, and shouldn't even exist as it's a sub-resource of playlist.
If you want to list all the available routes just run a rake routes and make sure the code references an existing path.

Answer 2

I didn't define the playlist that the song belongs to.
Adding to the controller
def create
#song = current_user.playlist.songs.new song_params
#song.playlist_id = #playlist.id
if #song.save
and
def find_playlist
#playlist = Playlist.find(params[:id])
end
then to simple form
<%= simple_form_for ([#playlist, #playlist.songs.build]) do |f| %>
It works.